Magnesium chloride particles with a polyhedral structure, catalytic components supported on these particles, resultant catalyst systems, processes for fabricating these products, and polyolefins obtained from these catalytic components

ABSTRACT

Porous particles of MgCl 2  having the form of essentially regular polyhedrons with six or eight faces in which the paired symmetrically opposite faces are essentially parallel, two of which faces are large and elongated and form the top face and the bottom face of a polyhedron such that on each of them the longest diagonal (D) is larger than the shortest distance (d) separating two opposite sides, which large elongated faces are surrounded essentially perpendicularly by the other essentially rectangular faces that form the sides of the said polyhedron, the length of the smaller side (e) of each of the said essentially rectangular faces being less than the shortest distance (d) separating the two opposite sides of the large elongated faces, catalytic components supported on the particles, catalyst systems utilizing the catalytic products, process for making the particles, and polyolefins obtained utilizing the catalytic systems.

BACKGROUND OF THE INVENTION

The present invention pertains to particles of preferably anhydrous,magnesium chloride (MgCl₂) in a new form as well as the process fortheir fabrication which overcome the disadvantages of spherical forms ofMgCl₂. These MgCl₂ particles can be employed as catalytic supports,particularly in Ziegler-Natta catalytic components. When these catalyticcomponents are employed as part of a catalyst system in thepolymerization of olefins, they preserve the morphology of the support.These catalytic components, catalyst systems utilizing the same are alsopart of the invention as are the processes for making these products andpolyolefins obtained by the use of the catalytic components.

SUMMARY OF THE INVENTION

The MgCl₂ in accordance with the invention is constituted of porousparticles which have, when viewed under a microscope, the form ofessentially regular polyhedrons with six or eight faces in which thepaired symmetrically opposite faces are essentially parallel two ofwhich faces are large and enlongated and form the top face and thebottom face of a polyhedron such that on each of them the longestdiagonal (D) is larger than the shortest distance (d) separating twoopposite sides, which large elongated faces are surrounded essentiallyperpendicularly by the other essentially rectangular faces that form thesides of the said polyhedron, the length of the smaller side (e) of eachof the said essentially rectangular faces being less than the shortestdistance (d) separating the two opposite sides of the large elongatedfaces.

Since the paired symmetrically opposite faces of a polyhedron areessentially parallel, the said faces can therefore be considered to beessentially geometrically identical.

The longest diagnonal (D) of each of the two large elongated faces of apolyhedron is usually from 10 to 100 μm in length. The shortest distance(d) separating two opposite sides of each of these two large faces isusually from 4 to 40 μm in length. The length of the smallest side (e)of each of the other faces forming the polyhedron, which length can alsobe considered to be the thickeness of the MgCl₂ particles, is usuallyfrom 2 to 20 μm. These particle dimensions are of course combined in amanner such as to respect the definition of the polyhedron and thereforeare preferably such that the ratio D/d is from 2 to 7 and the ratio d/eis from 1 to 3.

The invention also comprises the process of making such MgCl₂, catalyticcomponents and catalysts utilizing such MgCl₂, and polyolefins obtainedwith catalysts utilizing such MgCl₂, all as hereinafter described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an MgCl₂ particle in accord with thepresent invention;

FIG. 2 is a perspective view of an alternate embodiment of an MgCl₂particle in accord with the present invention;

FIG. 3 is a photomicrograph of an MgCl₂ particle in accord with thepresent invention in the form of an eight-face polyhedron;

FIG. 4 is a photomicrograph of an MgCl₂ particle in accord with thepresent invention in the form of a six-face polyhedron;

FIG. 5 is a photomicrograph of a group of MgCl₂ particles in accord withthe present invention;

FIG. 6 is a photomicrograph of a group of MgCl₂ particles subjected togrowth treatment in accord with the present invention; and

FIG. 7 is a photomicrograph of a group of catalytic component particlesin accord with the present invention.

DETAILED DESCRIPTION

The MgCl₂ of the present invention is generally constituted of more than90%, by number, of particles formed of a mixture of polyhedra as definedwith six and eight faces. However, it cannot be excluded that thepercentage of particles that do not respond to the definition are infact residues of strata originating from polyhedra that were more orless broken in handling or agglomerates of particles in accordance withthe invention.

The instant MgCl₂ particles have low porosity. The porosity can be from0.1 to 1 cm³ /g, preferably from 0.1 to 0.8 cm³ /g. Their specificsurface is usually from 0.5 to 10 m² /g, preferably from 1 to 3 m² /g.

The mean size of the MgCl₂ particles measured by the Malvern techniqueis generally from 10 to 100 μm, providing a narrow granulometry. Thebreadth of granulometric distribution expressed as ##EQU1## is usuallylower than 15 and more generally lower than 10. D90 is a diameter ofwhich 90% by weight of the particles are smaller and D10 is the diameterof which 10% by weight of the particles are smaller.

The MgCl₂ particles are obtained by suspending preferably anhydrousMgCl₂ in one of its complexing solvents, with the molar ratio of solventto MgCl₂ being lower than the solubility ratio of these two substancesat the temperature of the suspension. In accordance with this procedure,it is therefore indispensable that the MgCl₂ remain in suspension in thecomplexing solvent that is supersaturated with MgCl₂. Under theseconditions, it is recommended that the medium remain biphasic and suchthat it contains a sufficient amount of complexing solvent to maintainthe MgCl₂ in suspension.

"Complexing solvent" as used herein means any chemical compound which isbasic in the Lewis base sense and which can form with MgCl₂ a complex ofdefined, stable stiochiometry even in the presence of an excess of thesaid solvent, and even in the pure solvent.

Tetrahydrofuran is preferably selected from among the solvents that areparticularly suitable for fabrication of MgCl₂ particles as previouslydefined.

Under the recommended operating conditions, the formation of thesuspension is carried out in the conventional manner by bringing intocontact with the complexing solvent, preferably under agitation, MgCl₂of any structure that is preferably anhydrous or of commercial gradepreferably with less than 53% water. The MgCl₂ is maintained insuspension for a sufficient period of time, on the order of severalhours, for the particles to be deeply swollen by the complexing solvent.In order to obtain the best results, it is recommended that operationsduring the entire procedure be performed essentially at a temperaturebetween (BP -30° C.) and (BP +40° C.), with BP being the boiling pointof the complexing solvent at atmospheric pressure. This treatment allowsthe rearrangement of the initial MgCl₂ particles.

The most obvious phenomena that are produced during the granulometricrearrangement are the disappearance of the fine particles and the largeparticles of the initial MgCl₂ with appearance of a specific form ofparticles such as previously defined and which have a narrowgranulometric distribution.

Once this particle rearrangement operation has been finished, the MgCl₂particles in suspension are separated from the saturated MgCl₂ solvent,possibly washed, e.g., with a hydrocarbon, and possibly dried thermallyand/or treated under vacuum or chemically to totally or partiallyeliminate the complexing solvent.

In order to obtain particles with large dimensions, it is recommended,after the particle rearrangement treatment, to subject the particles toa growth treatment. This growth treatment can be comprised of adding tothe medium of particles in suspension in the saturated MgCl₂ solvent,essentially simultaneously on the one hand a solution of MgCl₂ incomplexing solvent, which can be identical to or different from that ofthe initial medium, and on the other hand an inert liquid which is anonsolvent of MgCl₂ and is miscible with the solvent, such as asaturated hydrocarbon. The best results are obtained when the additionis made in a manner such that the ratio of the flow rate of the solutionof MgCl₂ in the complexing solvent to the flow rate of the inert liquidis constant. This ratio is usually between 20 and 0.2, and preferablybetween 10 and 0.5.

If necessary, in order to reduce the solubility of the MgCl₂ in theinitial medium, it is possible to add to the medium of MgCl₂ particlesin suspension in the saturated MgCl₂ solvent, prior to the essentiallysimultaneous addition of saturated MgCl₂ solution and inert liquid, aninert liquid which is a nonsolvent of MgCl₂ and miscible with thecomplexing solvent of MgCl₂.

The operation is usually performed between room temperature and 80° C.The volume of MgCl₂ solution added to the medium determines the finalsize of the particles, since the MgCl₂ of the added solutioncrystallized on the initial particles of the medium, thereby increasingtheir size without changing their morphology.

The MgCl₂ recovered is in the form of MgCl₂, nX complex, in which X isthe solvent of MgCl₂ which has complexed it. The value of "n" whichrepresents the molar ratio ##EQU2## can obviously be equal to zero ifthe solvent was completely eliminated from the MgCl₂. This value of "n"usually ranges from 0 to 3. For example, in the specific case in whichtetrahydrofuran is used as the complexing solvent, the recommended valueof "n" is less than or equal to 2.5. After drying the complex, thisvalue is less than or equal to 1.5.

This MgCl₂ in the form of a complex with the "complexing solvent" can beused as is in the case in which it serves as transition-metal supportfor Ziegler-Natta catalyst components.

For the creation of the MgCl₂ suspension, the term complexing solvent isunderstood to mean not only the use of a single complexing solvent butalso the mixture of several of these compounds. It is possible to add tothe complexing solvent a miscible compound, which is inert in relationto the complexing solvent, such as a hydrocarbon containing from 6 to 30carbon atoms and which can be selected from among the saturated orunsaturated, straight or cyclical chain hydrocarbons such as heptane,cyclohexane, toluene, benzene or their derivatives such as durene orxylene or from among compounds with one or more hetroatoms such as theethers, esters, amines and silanes.

X-ray examination of the MgCl₂ -based molecular compound shows that itis a crystalline product.

Specifically, the X-ray diffraction spectrum of the compound MgCl₂, 1.5THF (tetrahydrofuran) exhibits the following principal diffractionlines:

    ______________________________________                                        2 θ position                                                                         Relative intensity                                               ______________________________________                                        9.25         59.9                                                             9.50         100.00                                                           16.96        15.5                                                             20.27        29.2                                                             22.45        23.76                                                            24.45        15.77                                                            25.27        24.98                                                            32.19        36.57                                                            32.34        19.02                                                            38.77        18.99                                                            39.77        18.53                                                            ______________________________________                                    

The half-height peak width, characteristic of the size of crystallites,is 0.169±0.006 for the line at 9.25 and 1.21±0.003 for the line at 9.50.

The measurements were performed with an INEL CPS-160 device, under avoltage of 40 kV and an intensity of 35 mA, using the Kα ray of a copperanticathode and silicon calibration. The INEL spectrum is indexed withthe PROLIX computer program and refined in accordance with the PEARSONVII profile.

Because of its original structure, the resultant MgCl₂ exhibits the sameadvantages as MgCl₂ in spherical form, but without its disadvantages.Specific sructures of MgCl₂ have been pursued in order to endow theMgCl₂ with good pourability, measured according to the standard ASTM D1895, and more specifically to endow the final polymer or copolymer withthis quality when the MgCl₂ is employed as catalytic support. Thespherical form was particularly desired in the case of catalysis so thatthe final polymer or copolymer particle, essentially reproducing in ahomethetic manner the particle of the support, would have thispourability quality. The drawback of this sphericity that it facilitatesthe accumulation of electrostatic charges in the reactors and conduits,causing, in particular, adhesion of powder to the walls. The structureof the MgCl₂ in accordance with the invention makes it possible toreduce this drawback.

A catalytic component of the Ziegler-Natta catalyst type can be obtainedessentially by combination of the MgCl₂ according to the invention witha transition-metal compound. Thus, this type of component can beobtained by depositing on the MgCl₂ a preferably halogenated titanium,vanadium, zirconium and/or hafnium compound, and more specificallyTiCl₄, TiCl₃, TiCl_(n) (OR)_(4-n) with 0≦n≦3 and R representing asaturated hydrocarbon radical with 1 to 12 carbons, VCl₃, VCl₄ or VOCl₃,HfCl₄ or ZrCl₄. This catalytic component associated with a cocatalystselected from among the organometallic compounds of the Group I-IIImetals in the periodic table and more specifically the aluminumcompounds, functions as a catalyst of the polymerization orcopolymerization of straight or branched chain olefins such as ethylene,propylene, butene-1, octene-1, 4-methyl-1-pentene, butadiene-1-3 and1-9-decadiene.

At least one electron donor can be added to the catalytic componentduring its fabrication and/or to the cocatalyst. The electron donor canbe selected, e.g., from among the Lewis bases, the esters and polyestersof oxygenated acids, the ethers and polyethers, the amines, the siliconcompounds such as the silanes and the alkylalkoxysilanes of formula SiR₁R₂ (OR)₂, SiR₁ (OR)₃ or SiR₁ R₂ R₃ (OR), in which the various R's arehydrocarbon radicals with 1 to 12 carbons, as well as the phosphoruscompounds such as the phosphates and phosphonates, with the preferredcompounds being the alkylated esters or polyesters of aromatic acids,the alkyl mono- or diethers, the alkoxysilanes and thealkylalkoxysilanes.

The catalyst obtained from the component fabricated from the MgCl₂ ofthe invention is suitable for all types of polymerization of olefins,high and low pressure, suspension, gas phase and bulk.

The catalytic component obtained from the MgCl₂ in accordance with theinvention is also constituted of particles which have, when viewed undera microscope, the form of essentially regular polyhedrons with six oreight faces in which the paired symmetrically opposite faces areessentially parallel, two of which faces are large and elongated andform the top face and the bottom face of a polyhedron such that on eachof them the longest diagonal (D) is larger than the shortest distance(d) separating two opposite sides, which large elongated faces aresurrounded essentially perpendicularly by the other essentiallyrectangular faces that form the sides of the said polyhedron, the lengthof the smaller side (e) of each of the said essentially rectangularfaces being less than the shortest distance (d) separating the twoopposite sides of the large elongated faces.

Since the paired symmetrically opposite faces of a polyhedron areessentially parallel, the said faces can therefore be considered to beessentially geometrically identical as shown in FIGS. 1 and 2.

The longest diagonal (D) of each of the two large elongated faces of apolyhedron is usually from 5 to 70 μm in length. The shortest distance(d) separating two opposite sides of each of these two large faces isusually from 2 to 30 μm in length. The length of the smallest (e) ofeach of the other faces forming the polyhedron, which length can also beconsidered to be the thickness of the particles of the catalyticcomponent, is usually from 1 to 10 μm. These dimensions of the particlesof the catalytic component are of course combined in a manner such as torespect the definition of the polyhedron and therefore are preferablysuch that the ratio D/d is from 2 to 7 and the ratio d/e is from 1 to 3.

The catalytic component is generally constituted of more than 90% bynumber of particles formed of a mixture of polyhedra as defined with sixand eight faces. However, it cannot be excluded that the percentage ofparticles that do not respond to the definition are in fact residues ofstrata originating from polyhedra that were more or less broken inhandling.

These particles of the catalytic component have an essentially smoothsurface; the porosity of these particles is generally from 0.1 to 1 cm³/g or preferably from 0.2 to 1.5 cm³ /g. The specific surface of thecatalytic component is usually from 1 to 600 m² /g or preferably from 1to 50 m² /g.

The mean size of the MgCl₂ particles measured by the Malvern techniqueis generally from 5 to 70 μm, preferably from 10 to 50 μm, providing anarrow granulometry. The breadth of granulometric distribution ##EQU3##as previously defined, is usually lower than 15 and more generally lowerthan 10.

The catalytic component can advantageously be prepared by impregnation,in a known manner, of the previously described MgCl₂ particles by atransition-metal compound that is liquid or in solution containing oneor more halogen atoms, particularly chlorine. Prior to this impregnationor at the same time, it can be recommended to carry out the depositingof at least one of the previously cited electron donors.

The resultant catalytic component, associated with a conventionalcocatalyst, usually selected from among the organaluminum compounds suchas the aluminoxanes, the aluminosiloxanes, the compounds with Al--R--Albonds in which R represents an alkyl group, or the compounds of formulaAlXqR's in which X represents Cl or OR' with R' designating a C₁ to C₁₆,preferably C₁ to C₁₂, alkyl radical while q and s are numbers such that1≦s≦3, 0≦q≦2 with q+s=3, forms a catalyst that is suitable for thepolymerization of olefins, more specifically of ethylene, propylene,butene-1, 4-methyl-1-pentene and hexene-1, octene, butadiene-1-3 ortheir mixtures. It is not excluded that one or more electron donors aspreviously defined by associated with the cocatalyst. The catalyticcomponent and the cocatalyst are associated in a catalyst system inproportions such that the molar ratio of the aluminum contained in thecocatalyst to the transition metal of the said component is between 0.5and 2,000, preferably between 1 and 1,000.

Polymerization of the previously cited olefins and, in general, C₂ toC₁₂ olefins individually or in mixtures by means of the previouslydefined catalytic system can be carried out in solution or suspension inan inert liquid medium, notably in an aliphatic hydrocarbon such asn-heptane, n-hexane, isohexane or isobutene, or in bulk in at least oneof the olefins to be polymerized maintained in the liquid orhypercritical state.

The operating conditions, notably temperatures, pressures and amount ofcatalytic system, for these liquid-phase polymerization are thoseconventional for similar cases employing supported or unsupportedconventional Ziegler-Natta catalytic systems.

For example, for polymerization performed in suspension or in a solutionin an inert liquid medium, one can operate at temperatures up to 250° C.and under pressures ranging from atmospheric pressure to 250 bars. Inthe case of polymerization in liquid propylene medium, the temperaturescan go as high as the critical temperature and the pressure can bebetween atmospheric pressure and the critical pressure. For bulkpolymerization or copolymerization of ethylene for the production ofpolyethylenes or copolymers that are predominantly ethylene, one canoperate at temperatures between 130° C. and 350° C. and under pressuresfrom 200 to 3,500 bars.

The catalytic system obtained by association of the transition-metalcomponent according to the invention with a cocatalyst and possibly anelectron donor as described above can also be used for the gas-phasepolymerization of the previously cited olefins or mixtures of theseolefins. Specifically, gas-phase polymerization, in contact with thesaid catalytic system, can be performed on a mixture of ethylene orpropylene and one or more C₂ to C₁₂ olefins such as ethylene, propylene,butene-1, hexene-1, 4-methyl-1-pentene and octene-1, containing when incontact with the catalytic system a molar proportion of C₂ to C₁₂comonomers between 0.1 and 90%, preferably between 1 and 60%.

Gas-phase polymerization of the olefin(s) in contact with the catalyticsystem can be performed in any reactor allowing gas-phase polymerizationand in particular in an agitated and/or fluidized bed reacator. Theconditions for performing the gas-phase polymerization, notablytemperature, pressure, injection of the olefin(s) into the agitatedand/or fluidized bed reactor and control of the polymerizationtemperature and pressure, are those conventionally used in the prior artfor gas-phase polymerization of olefins. Operations are generallycarried out at a temperature lower than the melting point MP of thepolymer or copolymer to be synthesized, more specifically between +20°C. and (MP -5)° C., and under a pressure such that the olefin(s), andpossibly the other hydrocarbon monomers present in the reactor, areessentially in vapor phase.

Solution, suspension, bulk or gas-phase polymerization can be carriedout in the presence of a chain-transfer agent so as to control the meltindex of the polymer or copolymer to be produced. The preferredchain-transfer agent is hydrogen, which is employed in an amount thatcan range up to 90%, preferably between 0.1 and 60%, of the volume ofthe totality of the olefins and hydrogen brought to the reactor.

The transition-metal component in accordance with the invention can alsobe used for the preparation of an active prepolymer which can be usedalone or in association with a cocatalyst selected from among thepreviously defined aluminum compounds.

The said active prepolymer is obtained by bringing into contact one ormore C₂ to C₁₂ alpha-olefins with a catalytic system formed byassociating the transition-metal component according to the inventionwith a cocatalyst selected from among the compounds cited above for thispurpose and employed in the previously specified proportions, the saidC₂ to C₁₂ olefins being used in an amount representing from 2 to 500grams, preferably from 2 to 100 grams, of C₂ to C₁₂ olefin(s) per gramof the transition-metal component.

The catalytic component in accordance with the invention is particularlyvaluable in the polymerization or copolymerization of ethylene orpropylene or their mixtures with each other or with another olefin, inthat it makes it possible to obtain polymers or copolymers with narrowgranulometry with the absence of fine particles, good pourability and amelt index suitable for the customary applications.

The resultant polyolefins or olefin copolymers are constituted ofparticles the mean size of which is generally between 100 and 3,000 μm,more particularly between 200 and 2,000 μm. The breadth of granulometricdistribution ##EQU4## of the powders is usually lower than 15, and moregenerally lower than 10, with their apparent density (AD) measuredaccording to the standard ASTM D 1895 method A, being between 0.3 and0.6 g/cm³, preferably between 0.4 and 0.5 g/cm³. The pourability of thepowders is high with values that are usually lower than or equal to 20seconds measured according to the standard ASTM D 1895. Their specificsurface is generally between 0.1 and 20 m² /g. Their porosity is between0.1 and 1 cm³ /g.

The photomicrographs (FIGS. 3 to 7) illustrate the different aspects ofthe invention.

FIG. 3 shows in 2,000× magnification a particle of MgCl₂ in the form ofan eight-face polyhedron.

FIG. 4 shows in 6,000× magnification a particle of MgCl₂ in the form ofa six-face polyhedron.

FIG. 5 shows in 150× magnification a group of MgCl₂ particles. More than90% of the MgCl₂ particles obtained responded to their definition.

FIG. 6 shows in 540× magnification particles that were subjected togrowth treatment.

FIG. 7 shows in 200× magnification a group of catalytic componentparticles.

The measurements of the mean diameters of the particles and the breadthof granulometric distribution ##EQU5## were performed with a Malvern1600 laser granulometer. The specific surface was determined by theisothermal physical adsorption of nitrogen at the temperature of liquidnitrogen, BET method, on an Quantasorb device. The porous volume wasdetermined by intrusion of mercury under pressure with an Erbascience1500 porosimeter. The measurements were performed after treatment of thesamples under vacuum for 2 hours at room temperature.

The invention will be further described in connection with the followingexamples which are set forth for further illustration of the invention.

EXAMPLE 1

The following were introduced under nitrogen into a 5-liter reactor withdouble-jacket thermal control and equipped at its bottom with afiltration plate and a mechanical blade agitator:

(i) 300 g of a commercial anhydrous mangesium chloride, containing 0.3%water with a mean dimension of 2 millimeters, and

(ii) 2 liters of tetrahydrofuran (THF).

The agitation was brought to 150 rpm and the temperature was brought to65° C.

After 7 hours of reaction, the suspension was filtered and the solidrecovered after washing with hexane and drying under a nitrogen streamwas comprised of 530 g of a granular white solid with good pourability,of molar composition MgCl₂, 1.5 THF and with an apparent of 0.59 g/cm³.

Granulometric analysis yielded the following values: mean particle sizeof 41 μm with a breadth of granulometric distribution expressed by theratio ##EQU6## of 4.3.

Examination under a scanning electronic microscope showed the particlesto have the form of polyhedra with 6 ot 8 faces as illustrated in FIGS.3 to 5.

EXAMPLE 2

The operating conditions of Example 1 were employed except that thereaction temperature was limited to 50° C. In the same manner, there wasobtained 525 g of dry support with an apparent density of 0.6, a meanparticle size of 45 μm and a breadth of granulometric distribution of5.0. The molar ratio of THF to MgCl₂ remained at 1.5. The morphology ofthe particles was retained.

EXAMPLE 3

Example 1 was repeated except that at the end of the reaction, butbefore filtration, there was slowly added 1 liter of heptane.

The dry solid which was recovered had the following characteristics:apparent density of 0.55, mean aprticle size of 44 μm and a breadth ofgranulometric distribution of 4.3. The morphology of the particles wasretained.

EXAMPLE 4

Example 1 was repeated with the THF replaced by a THF/heptane mixture at20% by weight of heptane.

The characteristics of the dry solid which was recovered were: apparentdensity of 0.60 g/cm³, mean particle size of 33 μm and a breadth ofgranulometric distribution 5.8. The morphology of the particles wasretained.

EXAMPLE 5

Example 1 was repeated with the THF replaced by a THF/heptane mixture at33% heptane. The dry solid had the following characteristics: apparentdensity of 0.59 g/cm³, particle size of 23 μm and a breadth ofgranulometric distribution of 6.0. The morphology of the particles wasretained.

EXAMPLE 6

Example 1 was repeated with the addition of 45 grams of1,2,4,5-tetramethylbenzene. After drying, the solid had the followingcharacteristics: apparent density of 0.6 g/cm³, mean particle size of 40μm and a breadth of granulometric distribution of 5.0. The morphology ofthe particles was retained.

EXAMPLE 7

Example 1 was repeated with THF replaced by a mixture of THF andtetrahydropyran (THP) at 10% of THP.

The solid recovered after drying had the following characteristics:apparent density of 0.22 g/cm³, mean particle size of 38 μm and abreadth of granulometric distribution 3.7. The morphology of theparticles was retained.

EXAMPLE 8

Example 1 was repeated with the addition of 300 g of diisobutylphthalate (DBP) and 45 g of 1,2,4,5-tetramethylbenzene to the MgCl₂ andTHF mixture.

After drying, the solid recovered had a molar composition (MgCl₂/THF/DBP) of (1/1/0.03). The apparent density was 0.65 g/cm³ and themean particle size 40 μm with a breadth of granulometric distribution of5.4. The morphology of the particles was retained.

EXAMPLE 9

Example 1 was repeated. The dry solid recovered was treated again with asolution of triethylaluminum in heptane such that the triethylaluminumconcentration was 20% by weight and the aluminum/THF molar ratio was 2.After 2 hours of reaction at 80° C., a solid was recovered which had thefollowing characteristics after drying: apparent density of 0.8 g/cm³, amean particle size of 30 μm and a breadth of granulometric distributionof 5. The molar ratio of THF to MgCl₂ was close to 0. The morphology ofthe particles was retained.

EXAMPLE 10

Example 1 was repeated. The dry granular solid was fluidized under anitrogen stream at atmospheric pressure and at a temperature of 150° C.for 4 hours.

The granula solid which was recovered had an apparent density of 0.45g/cm³ with a mean particle size of 32 μm and a breadth of granulometricdistribution of 6. The morphology was retained. The molar ratio of THFto MgCl₂ was 0.2.

EXAMPLE 11

To 13.8 g of solid prepared as described in Example 1 were added 30 mLof heptane and 2.5 mL of di-n-butyl phosphate. This was agitated for 2hours at 100° C. After reaction, 40 mL of pure TiCl₄ was added and thereaction was continued for 2 additional hours at the same temperature.At the end, the temperature was reduced to 80° C., the solid wasdecanted and the supernatant phase was siphoned off. The solid was takenup twice in a solution of TiCl₄ in 1-2-dichloroethane at 10% by volumeof TiCl₄ at 85° C. for 2 hours. After decanting and siphoning, the solidwas washed with hexane at room temperature. The catalytic solid was thendried under vacuum at room temperature until a dry powder with goodpourability was obtained. Analysis of the solid showed 2.5% titanium,20% of magnesium and 67.6% of chlorine. Granulometric anlaysis of thecatalytic solid showed a mean particle diameter of 32 μm and a breadthdefined by the ratio ##EQU7## of 4.0. The morphology of the particles ofthe catalytic solid was identical to that of the support and as shown inFIG. 7.

EXAMPLE 12

Ten grams of the support prepared in accordance with Example 6 weresuspended in heptane to which di-n-butyl phthalate was then added suchthat the diester concentration was 0.4 M/l and the molar ratioTHF/diester was 7.

The reaction was allowed to continue for 3 hours at 80° C. underagitation. The suspension was then filtered after which 100 mL of pureTiCl₄ was added and agitation was continued for 2 hours at 90° C. Afteranother filtration, 5 washings were performed with 100 mL of a solutionof TiCl₄ in 1-2-dichloroethane at 10% by volume of TiCl₄ ; each washingwas carried out for 1 hour at 80° C.

After filtration, the solid was washed with hexane and dried under anitrogen current at 80° C. A yellow-green solid was recovered, analysisof which showed levels of Ti, Mg and Cl of 2.3, 19.5 and 65% by weight,respectively. The mean diameter of the particles was 26 μm and thegranulometric breadth was 4.3. The morphology of the particles wascomparable to that illustrated in FIG. 7.

EXAMPLE 13

The following were introduced under a stream of gaseous propylene into a1.5-liter stainless steel reactor equipped with an anchor agitator withmagnetic drive and double-jacket thermal control: 1 liter of heptane, 6mmoles of triethylaluminum and 0.6 mmole of cyclohexyl methyldimethoxysilane. 15 mg of the catalytic solid prepared in accordancewith Example 11 was then introduceed along with 50 ml of gaseoushydrogen. The temperature was brought to 70° C. Gaseous propylene wasintroduced at the rate of 4 relative bars. During the entire reaction,the pressure of the reactor was maintained by a continuous supply ofmonomer.

At the end of 90 minutes of reaction, the temperature was reduced to 20°C. and the pressure was reduced to atmospheric pressure.

The polymer, which was insoluble in heptane, was recovered byfiltration, dried and weighed. The heptane solution was evaporated so asto recover any possibly solubilized polymer.

The 50.4 grams of granular powder obtained in this manner had very goodpourability, a mean particle diameter of 400 μm and a breadth ofgranulometric distribution of 4.5. 0.6 gram of soluble polypropylene wasrecovered from the heptane solution. After extraction with the Kumagawaapparatus with heptane of the soluble polymer from the preceding powder,a total index of isotacticity of 97.7% was calculated. The melt indexmeasured according to the standard ASTM D 238 method L was 3.5. Theapparent density measured according to the standard ASTM D 1895 method Awas 0.40 and the pourability was 18 seconds.

EXAMPLE 14

The following were introduced, in order, at 30° C. into an 8-literthermostated reactor equipped with a blade agitator and magnetic drive:2.4 liters of gaseous hydrogen, 6 liters of liquid propylene, 18 mM oftriethylaluminum and 1.8 mM of cyclohexyl methyl dimethoxysilane. Aftera precontact of 10 minutes, 70 mg of the catalytic component describedin Example 12 was injected into the reactor. The temperature was broughtquickly to 70° C. and maintained at this value for 1 hour.

At the end of the reaction, the reactor was cooled down and the pressurelowered to atmospheric pressure. The 2250 grams of granular solid whichwere recovered had excellent pourability (17) seconds according tostandard ASTM D 1895), a high apparent density 0.47 (standard ASTM D1895 method A) and an isotacticity index, measured by extraction withheptane of the amorphous polymer with a Kumagawa apparatus, of 97.8% byweight. The melt index of the polymer measured according to standardASTM D 1238 method L was 2.9.

The polymer had the following characteristics: a mean particle diameterof 900 μm and a breadth of granulometric distribution of 5. The ratioD/d of the majority of particles is between 1.5 and 2.5.

EXAMPLE 15

Example 1 was repeated with the replacement of the THF by a mixture ofTHF/EDIA (diisoamyl ether) in a 14/1 ratio by volume. Thecharacteristics of the solid recovered were: apparent density of 0.559g/cm³, mean particle size of 50 μm and a ##EQU8## breadth ofgranulometric distribution of 5.7. The morphology of the particles wasretained.

EXAMPLE 16

Example 1 was repeated with the replacement of the THF by a mixture ofTHF/PMHS (polymethylhydrogensiloxane) in a ratio of 15/1 by volume.

The characterstics of the solid recovered were: apparent density of 0.5g/cm³, mean particle size of 37 μm and a ##EQU9## breadth ofgranulometric distribution of 6.6. The morphology of the particles wasretained.

EXAMPLE 17

100 mL of pure TiCl4 was added to 20 g of the solid prepared inaccordance with Example 1. Agitation was then carried out for 1 hour at90° C., followed by eight washings at 80° C. with 50 Ml of a 10/90 byvolume mixture of TiCl4/DCE (dichloroethane). After these treatment werefinished, washing with 100 cc of hexane was carried out twice. The solidwas isolated by filtration and then dried under a nitrogen stream at 50°C.

Analysis of the catalytic solid showed a Ti content of 3.8%, a Mgcontent of 61.2% and a Cl content of 61.2%. The mean diameter of theparticles of the catalytic solid was 27 μm and the breadth ofgranulometric distribution was 3.9.

EXAMPLE 18

The following were introduced at 40° C. under a nitrogen stream into thereactor described in Example 13:1 liter of hexane, 6 mM oftriisobutylaluminum and 20 mg of the catalyst obtained in accordancewith Example 17. The nitrogen pressure was raised to 2 bars of totalpressure and the temperature was brought to 80° C. When temperatureequilibrium was reached, the pressure was adjusted to 3 bars bysupplying nitrogen. Four relative bars of hydrogen and six bars ofethylene were added. The pressure was maintained constant at 13 barsabsolute by adding ethylene.

At the end of 120 minutes of reaction, the temperature was decreased to40° C. and the reactor was decompressed to atmospheric pressure. Afterfiltration and drying, 646 g of polymer were recovered.

The productivity was 22,275 g of PE/g of catalyst and the mean particlediameter of the powder was 542 microns for an apparent density of 0.319g/cm³.

The melt indices at 190° C. under loads of 2.16 kg and 5 kg were 0.7 and4.68, respectively.

EXAMPLE 19

Operations were performed as in Example 18 except that 20 mg of thecatalyst prepared in Example 11 was introduced.

The polyerization reaction was continued for 180 minutes and 405 g ofpolyethylene was recovered at the end of the reaction, i.e., aproductivity of 20,250 g of polymer ws 521 microns for an apparentdensity of 0.311 g/cm³.

The melt indices at 190° C. under loads of 2.16 kg and 5 g were 0.87 and2.85, respectively.

EXAMPLE 20 a) Synthesis of a prepolymer

The following were introduced under a nitrogen stream at 40° C. into areactor of the same type as was used in Example 13:

0.8 liter or dry hexane

14 mM of THA (trihexylaluminum)

1 g of the catalyst obtained in Example 11

One then introduced:

2 relative bars of hydrogen

A controlled flow of ethylene was then introduced in accordance with thefollowing schedule:

1.2 L/h for 30 minutes

2 L/h for 30 minutes

4 L/h for 30 minutes

8 L/h for 30 minutes

16 L/h for 30 minutes

30 L/h for 130 minutes

The reactor was decompressed and the hexane was evaporated under anitrogen stream at 70° C. The 94 g of prepolymer that was collected hada degree of prepolymerization of 94 g of PE/g of catalyst.

b) Gas-phase synthesis of a high-density polyethylene (HDPE)

Operations were performed in a dried 8.2-liter, thermostated reactorequipped with agitation in the presence of 20 g of a dispersant chargeof polyethylene originating from an identical prior test.

Into this reactor, which was maintained at 90° C. during the entirepolymerization, under agitation of 400 rpm and a vacuum of 1.33 Pa,hydrogen was injected until reaching a pressure of 6 bars absolute.Eight bars of ethylene were then injected into the reactor untilreaching partial pressures of hydrogen and ethylene of 6 and 8 barsabsolute, respectively.

After these injections, 4 g of the active prepolymer prepared above wasinjected by nitrogen pressure; the injection of nitrogen was continueduntil the total pressure inside the reactor reached 21 bars absolute.The pressure was maintained at this level by injection of ethylene.After 120 minutes of reaction, the polymerization was stopped bydecompression of the reactor which was then purged with nitrogen andallowed to cool.

Including the initial charge, 369 g HDPE powder was recovered. Theproductivity was 7,920 g of PE/g of catalyst. The powder had a meanparticle diameter of 495 microns and an apparent density diameter of 495microns and an apparent density of 0.359 g/cm³. The melt indices underloads of 2.16 kg and 5 kg were 4.55 and 14.6, respectively.

c) Gas-phase systhesis of an ethylene/butene-1 copolymer

Operations were carried out in a dried 8.2-liter, thermostated reactorequipped with blade agitation in the presence of 20 g of polyethylenepowder originating from an idential prior test. Into this reactor,maintained at 85° C. during the entire polymerization, under agitationof circa 400 rpm and a vacuum of 1.33 Pa, was injected butene-1 until apressure of 1 bar absolute was reached. The injection of butene-1 wascontinued until the pressure had climbed to 1.5 bars absolute.

One then injected successively into the reactor 1 bar of hydrogen and4.5 bars of ethylene until reaching partial pressures of hydrogen andethylene of 1 and 1.5 bars, respectively. After these injections, 3 g ofactive prepolymer was introduced by nitrogen pressure with the injectionof nitrogen being continued until the total pressure inside the reactorreached 21 bars absolute. The pressure was maintained at this value bythe introduction of butene-1/ethylene in a molar ratio of 0.0466. After120 minutes of reaction, the polymerization was stopped by decompressionof the reactor, which was then purged with nitrogen and allowed to cool.

Including the initial charge, 372 g of ethylene/butene-1 copolymer wasobtained. The productivity was 11,00 g of PE/g of catalyst and thedensity was 0.918 g/cm³. The powder had a mean particle diameter of 407microns and an apparent density of 0.290 g/cm³. The melt indices at 190°C. under loads f 2.16 kg and 21.6 kg were 1.35 and 47.1, respectively.

EXAMPLE 21

The following were added at 80° C. under agitation of circa 100 rpm to a1-liter reactor equipped with an agitator and a coolant-circulationdouble-jacket temperature control:

1.3M of anydrous MgCl₂

0.098M of durene

9M of THF

Agitation was performed for 1.5 hours at 100 rmp and then for 2.5 hoursat 250 rpm.

The suspension was transferred to a Schlenk tube. An aliquot of thissuspension was filtered and washed with hexane for analysis of the solid(S1) obtained.

The reactor was charged with an aliquot of the suspension obtained,which contained 90 mM of MgCl₂, 623 mM of THF and 6.78 mM of durene.Under agitation of circa 150 rpm at a temperature of 60° C., anequivalent volume of hexane was added over 30 minutes.

Continuing the agitation, the following were added simultaneously over2.5 hours at 60° C.;

a 514-mL flow of a saturated solution at 60° C. of MgCl₂ in THFcontaining 20 g of MgCl₂, and

a 514-mL flow of hexane.

At the end of growth, the suspension was cooled to room temperature andthen filtered. The support was washed three times with 500 mL of hexaneand dried at 50° C. under a nitrogen stream. The support (S2) wastransferred to a Schlenk tube under nitrogen. 58 g of MgCl₂, 1.5 THFcomplex was isolated.

    ______________________________________                                         SupportRef.                                                                              D90     diameterMean                                                                              D10                                                                                ##STR1##                                 ______________________________________                                        S1         94.1    49.55       17.28                                                                              5.4                                       S2         111.6   60.4        23.43                                                                              4.8                                       ______________________________________                                    

Viewed under a scanning electron microscope, the particles had theappearance shown in FIG. 6.

While the invention has been described in connection with a preferredembodiment, it is not intended to limit the scope of the invention tothe particular form set forth, but on the contrary, it is intended tocover such alternatives, modifications, and equivalents as may beincluded within the spirit and scope of the invention as defined by theappended claims.

What is claimed is:
 1. Porous particles of MgCl₂ having the form ofessentially regular polyhedrons with six or eight faces in which thepaired symmetrically opposite faces are essentially parallel, two ofwhich faces are large and elongated and form the top face and the bottomface of a polyhedron such that on each of them the longest diagonal (D)is larger than the shortest distance (d) separating two opposite sides,which large elongated faces are surrounded essentially perpendicularlyby the other essentially rectangular faces that form the sides of thesaid polyhedron, the length of the smaller side (e) of each of the saidessentially rectangular faces being less than the shortest distance (d)separating the two opposite sides of the large elongated faces.
 2. Theparticles of claim 1, wherein the paired symmetrically opposite facesare geometrically essentially identical.
 3. The particles of claim 2,where in the ratio (D)/(d) is between 2 and
 7. 4. The particles of claim3, wherein the ratio (d)/(e) is between 1 and
 3. 5. The particles ofclaim 4, wherein (D) is between 10 and 100 μm, (d) is between 4 and 40μm, and (e) is between 2 and 20 μm.
 6. The particles of claim 5, whereintheir porosity is between 0.1 and 1 cm³ /g.
 7. The particles of claim 6,wherein their specific surface is between 0.5 and 10 m² /g.
 8. Theparticles of claim 7, wherein the size of the particles is between 10and 100 m with a breadth of granulometric distribution ##EQU10## lessthan
 15. 9. The particles of claim 8, wherein the MgCl₂ is in the formof a MgCl₂, nX complex in which X is the solvent of MgCl₂ with which itis complexed, with n being such that the amount by weigh t of solventcomplexed with the MgCl₂ allows the complex to retain its crystallineform.
 10. The particles of claim 9, wherein n has a value between 0 and3.
 11. The process of making porous MgCl₂ in crystalline form ofessentially six or eight face polyhedrons comprising suspending MgCl₂ inat least one of its complexing solvents with the molar ratio of thesolvent to MgCl₂ being lower than the solubility ratio of these twosubstances at the temperature of the suspension.
 12. The process ofclaim 11, wherein the suspension is a biphasic medium such that itcontains an amount of complexing solvent that is sufficient to maintainthe MgCl₂ in suspension.
 13. The process of claim 12, wherein thesuspension is maintained essentially at the boiling point of thecomplexing solvent without dropping more than 30° C. below this boilingpoint.
 14. The process of claim 13, wherein in order to increase thesize of the particles without changing their morphology, there is addedessentially simultaneously to the suspension a solution of MgCl₂ in acomplexing solvent and an inert liquid which is a nonsolvent of MgCl₂and is miscible with the complexing solvent.
 15. A catalytic componentconsisting essentially of particles of MgCl₂ impregnated by atransition-metal compound and up to an effective amount of an electrondonor, wherein said particles have the form of essentially regularpolyhedrons with six or eight faces in which the paired symmetricallyopposite faces are essentially parallel, two of which faces are largeand elongated and form the top face and the bottom face of a polyhedronsuch that on each of them the longest diagonal (D) is larger than theshortest distance (d) separating two opposite sides, which largeelongated faces are surrounded essentially perpendicularly by the otheressentially rectangular faces that form the sides of the saidpolyhedron, the length of the smaller side (e) of each of the saidessentially rectangular faces being less than the shortest distance (d)separating the two opposite sides of the large elongated faces.
 16. Thecatalytic component of claim 15, wherein the paired symmeticallyopposite faces are geometrically essentially identical.
 17. Thecatalytic component of claim 16, wherein the ratio ##EQU11## is between2 and
 7. 18. The catalytic component of claim 17, wherein the ratio##EQU12## is between 1 and
 3. 19. The catalytic component of claim 18,wherein (d) is between 5 and 70 μm, (d) is between 2 and 30 μm, and (e)is between 1 and 10 μm.
 20. The catalytic component of claim 19, whereinthe porosity of its particle is between 0.1 and 2 cm³ /g.
 21. Thecatalytic component of claim 20, wherein its specific surface is between1 and 600 m² /g.
 22. The catalytic component of claim 21, wherein thesize of its particles is between 5 and 70 m with a breadth ofgranulometric distribution ##EQU13## lower than
 15. 23. A catalyticsystem for the polymerization of olefins consisting essentially of acatalytic component of anyone of claims 15 to 22 and a cocatalystconsisting essentially of a organoaluminum compound.